Tuberculosis(TB) is the leading cause of death from any single infectious agent for much of the world. Globally, it is estimated that one third of the world's population carries a latent TB infection. Most alarming are the outbreaks of multi-drug-resistant TB. Rifampicin is currently a treatment of choice, but there is a growing resistance of mycobacteria to rifampicin and its analogs and therefore an important need for new therapies. The goal of this research program is to discover novel classes of antibiotics for the treatment of drug-resistant mycobacteria. A high throughput drug screen will be established for the discovery of new inhibitors of rifampicin-resistant RNA polymerase of M. tuberculosis and M. avium. Using purified M. smegmatis as a model system, RNA polymerase resistant to rifampicin and rifabutin will be selected, purified and used to develop a robust, reliable assay for screening a library of synthetic organic compounds and natural products for compounds which inhibit RNA polymerase. Once active compounds have been identified, they will be screened for potency, specificity and toxicity, and promising compounds will ultimately be developed into antimicrobial agent through medicinal chemistry. PROPOSED COMMERCIAL APPLICATION: It is estimated that 7% of all deaths and 26% of all preventable deaths may be due to TB (Snider and Montagne, 1994). There is a growing resistance of M. tuberculosis to multiple drugs, including rifampicin, which is a first line therapeutic agent that inhibits RNA polymerase enzyme activity. Novel antimicrobial agents discovered by the high volume screen proposed in this plan will lead to a novel treatment for drug-resistant mycobacterial infections.